This invention relates to blade assemblies for vibrator motors, and more particularly to blade assemblies for hair clippers, and the like, that are configured to reduce the likelihood of nicking or cutting a subject""s skin.
Vibrator motors have been used in electric hair clippers for many years, as in U.S. Pat. Nos. 2,877,364, 2,986,662 and 3,026,430, which are hereby incorporated by reference in their entirety. One example of a conventional vibrator motor in a hair clipper is shown in FIG. 5. Of course, there are other types and models of hair clippers other than that shown in FIG. 5 that also include vibrator motors. Referring back to FIG. 5, this figure shows a hair clipper 10 that includes a case 12, a stationary hair cutting blade 14, and a reciprocating hair cutting blade 16. The blade 16 is driven by a vibrator motor 18, which includes a stationary coil 20, coil laminations 22 and moving laminations 24. It should be noted that in some models, a moving steel arm is utilized in place of the moving laminations 24.
The coil laminations 22 are stationary within the case 12. The moving laminations 24 are part of a vibrating arm 26. The vibrating arm 26 also includes a tail bracket 28. The arm 26 is operatively connected to the moving blade 16 through a resilient finger 32. A mechanical spring system 34 includes the tail bracket 28, which is fixed at one end to the case 12, and coil springs 36 located on each side of the tail bracket 28 and between adjacent walls of the case 12. The mechanical spring system 34 is designed so that the vibrating arm 26 has an appropriate resonant frequency.
In operation, the arm laminations 24 tend to reciprocate in a slight arc because the vibrating arm 26 is fixed at one end. As a result, the moving blade 16 tends to reciprocate along an elliptical path A. As will be explained below, the elliptical path of the moving blade 16 contributes to the problem addressed by the present invention.
While the conventional hair clippers just described have been useful and commercially successful, cutting or nicking a subject""s skin can be a problem. Specifically, hair clippers are sometimes used to cut close to the scalp, with the tips of the blade teeth being placed directly against the scalp. However, due to the elliptical path of the cutting blade, there is a tendency for the cutting blade to extend beyond the stationary blade towards the end of the blade""s stroke, resulting in cutting or nicking of a subject""s skin. By manner of illustration, FIG. 6A is a front view of a conventional cutting assembly, and FIG. 6B is an enlarged fragmentary view of FIG. 6A showing the cutting blade 16 extending beyond the stationary blade 14 towards the end of the cutting stroke.
To address the above-described problem, in some conventional hair clippers, the length of the stationary blade 14 is increased with respect to the length of the moving blade in order to increase the size of an overlap, XGap (shown toward the left of FIG. 6A), which is measured between the end of the cutting blade 16 and end of the stationary blade 14. Notably, if the overlap XGap is sufficiently great, then the cutting blade 16 will not extend beyond the stationary blade 14 at the end of the cutting stroke. Unfortunately, in order to provide an extremely close cut, it is desirable to reduce XGap to approximately zero.
Alternatively, some conventional hair clippers incorporate a blade guide into the device in order to ensure that the cutting blade travels in a straight line, without extending beyond the stationary blade. This approach provides satisfactory results, but results in higher manufacturing costs, making this approach unsuitable for low cost hair clippers. Moreover, the blade guide imposes a side load on the reciprocating blade, which undesirably reduces the cutting power in a vibrator type clipper.
Yet another approach to the above-described problem involves reducing the stroke of the cutting blade. As described above, the cutting blade is most likely to extend beyond the stationary blade at the extreme end of the stroke. Thus, the likelihood of the stationary blade extending beyond the stationary blade may be reduced by, for example, reducing the ampere-turns of the motor. However, reducing the stroke of the blade in this manner can also reduce cutting performance to an unacceptable level.
Thus, there is a need for a blade assembly for hair clippers which provides an extremely close cut while avoiding pinching or nicking of the skin. There is also a need for blade assemblies which are inexpensive to manufacture, and which avoid the use of rigid guide paths. Another need is for an improved blade assembly for vibrator hair clippers, where the improved blade assembly can be easily incorporated in existing product designs.
Accordingly, one object of this invention is to provide new and improved blade assemblies for vibratory hair clippers.
Another object is to provide new and improved blade assemblies which provide a close cut without the use of a rigid blade guide.
Yet another object is to provide new and improved blade assemblies which provide a close cut without sacrificing cutting power.
Still another object is to provide new and improved blade assemblies which are simple to make and assemble, and which can be easily adapted for use in conventional vibrator hair clippers.
Briefly, the present invention relates, in part, to a blade assembly for an electric hair cutter, where the blade assembly includes a stationary blade and a cutting blade. The stationary blade includes a plurality of stationary cutting teeth, with each of the stationary cutting teeth having a tip at a distal end thereof, and wherein the tips of the stationary cutting teeth define a first imaginary line. The cutting blade is configured for reciprocating arcuate motion relative to the stationary blade, and has a plurality of reciprocating cutting teeth, with each of the reciprocating cutting teeth having a tip at a distal end thereof. The tips of the reciprocating cutting teeth define a second imaginary line. One important feature of the present invention is that the distance between the first imaginary line and the second imaginary line is greater near both end portions thereof than a corresponding distance at a center portion between the end portions.
The increased distance near the end portions may be realized in any of several different ways. For example, the tip heights of the reciprocating cutting teeth may gradually increase from each of the first and second ends toward the midpoint, whereby the tooth tips define the second imaginary line in the form of an arc. Alternatively, the tip heights of the reciprocating cutting teeth near both the first and second ends only may be shorter than the tip heights of the reciprocating cutting teeth near the midpoint, such that a group of the reciprocating cutting teeth near the midpoint are all of a uniform tip height.
According to another embodiment of the present invention, the cutting teeth height configurations of the stationary blade and the cutting blade are transposed. Specifically, tip heights of the stationary cutting teeth proximate one of the first and second ends are longer than the tip heights of the cutting teeth proximate a midpoint between the first and second ends. In this embodiment, the first imaginary line is thus preferably in the form of a generally concave arc, either with or without a straight center portion.
As a further alternative, both the first and the second imaginary lines may be configured so that neither line is a generally straight line. Preferably, the first imaginary line is generally concave and the second imaginary line is generally convex. Optionally, either one of, or both, the first imaginary line and the second imaginary line may also include a straight portion near the center thereof.
Each of the above described embodiments provides a closer cut than possible with traditional hair clipper blades, without sacrificing cutting power or increasing the cost of manufacture.